Not Applicable
Not Applicable
1. Description of Related Art
Microorganisms adhere to a wide variety of surfaces, particularly surfaces in contact with aqueous fluids which provide a suitable environment for microbial growth. For example, microorganisms are known to adhere to ship hulls, marine structures, teeth, medical implants, cooling towers, and heat exchangers. Adhering to such submerged or submergible surfaces, microorganisms may foul the surface or cause it to deteriorate.
In mammals, (e.g., humans, livestock, pets), microorganisms adhered to a surface may lead to health problems. Plaque, for example, results from microorganisms adhering to the surfaces of teeth. Medical implants with unwanted microorganisms adhered to their surfaces often become crusted over and must be replaced.
Scientific studies have shown that the first stage of biofouling in aqueous systems is generally the formation of a thin biofilm on submerged or submergible surfaces, i.e., surfaces exposed to the aqueous system. Attaching to and colonizing on a submerged surface, microorganisms such as bacteria, are generally thought to form the biofilm and modify the surface to favor the development of the more complex community of organisms that make up the advanced biofouling of the aqueous system and its submerged surfaces. A general review of the mechanisms of the importance of biofilm as the initial stage in biofouling is given by C. A. Kent in xe2x80x9cBiological Fouling: Basic Science and Modelsxe2x80x9d (in Melo, L. F., Bott, T. R., Bernardo, C. A. (eds.), Fouling Science and Technology, NATO ASI Series, Series E, Applied Sciences: No. 145, Kluwer Acad. Publishers, Dordrecht, The Netherlands, 1988). Other literature references include M. Fletcher and G. I. Loeb, Appl. Environ. Microbiol. 37 (1979) 67-72; M. Humphries et al., FEMS Microbiology Ecology 38 (1986) 299-308; and M. Humphries et. al., FEMS Microbiology Letters 42 (1987) 91-101.
Biofouling, or biological fouling, is a persistent nuisance or problem in a wide variety of aqueous systems. Biofouling, both microbiological and macrobiological fouling, is caused by the buildup of microorganisms, macroorganisms, extracellular substances, and dirt and debris that become trapped in the biomass. The organisms involved include microorganisms such as bacteria, fungi, yeasts, algae, diatoms, protozoa, and macroorganisms such as macroalgae, barnacles, and small mollusks like Asiatic clams or Zebra Mussels.
Another objectionable biofouling phenomenon occurring in aqueous systems, particularly in aqueous industrial process fluids, is slime formation. Slime formation can occur in fresh, brackish or salt water systems. Slime consists of matted deposits of microorganisms, fibers and debris. It may be stringy, pasty, rubbery, tapioca-like, or hard, and have a characteristic, undesirable odor that is different from that of the aqueous system in which it formed. The microorganisms involved in slime formation are primarily different species of spore-forming and nonspore-forming bacteria, particularly capsulated forms of bacteria which secrete gelatinous substances that envelop or encase the cells. Slime microorganisms also include filamentous bacteria, filamentous fungi of the mold type, yeast, and yeast-like organisms.
Biofouling, which often degrades an aqueous system, may manifest itself as a variety of problems, such as loss of viscosity, gas formation, objectionable odors, decreased pH, color change, and gelling. Additionally, degradation of an aqueous system can cause fouling of the related water-handling system, which may include, for example, cooling towers, pumps, heat exchangers, and pipelines, heating systems, scrubbing systems, and other similar systems.
Biofouling can have a direct adverse economic impact when it occurs in industrial process waters, for example in cooling waters, metal working fluids, or other recirculating water systems such as those used in papermaking or textile manufacture. If not controlled, biological fouling of industrial process waters can interfere with process operations, lowering process efficiency, wasting energy, plugging the water-handling system, and even degrade product quality.
For example, cooling water systems used in power plants, refineries, chemical plants, air-conditioning systems, and other industrial operations frequently encounter biofouling problems. Airborne organisms entrained from cooling towers as well as waterborne organisms from the system""s water supply commonly contaminate these aqueous systems. The water in such systems generally provides an excellent growth medium for these organisms. Aerobic and heliotropic organisms flourish in the towers. Other organisms grow in and colonize such areas as the tower sump, pipelines, heat exchangers, etc. If not controlled, the resulting biofouling can plug the towers, block pipelines, and coat heat-transfer surfaces with layers of slime and other biologic mats. This prevents proper operation, reduces cooling efficiency and, perhaps more importantly, increases the costs of the overall process.
Industrial processes subject to biofouling also include papermaking, the manufacture of pulp, paper, paperboard, etc. and textile manufacture, particularly water-laid non-woven textiles. These industrial processes generally recirculate large amounts of water under conditions which favor the growth of biofouling organisms.
Paper machines, for example, handle very large volumes of water in recirculating systems called xe2x80x9cwhite water systems.xe2x80x9d The furnish to a paper machine typically contains only about 0.5% of fibrous and non-fibrous papermaking solids, which means that for each ton of paper almost 200 tons of water pass through the headbox. Most of this water recirculates in the white water system. White water systems provide excellent growth media for biofouling microorganisms. That growth can result in the formation of slime and other deposits in headboxes, waterlines, and papermaking equipment. Such biofouling not only can interfere with water and stock flows, but when loose, can cause spots, holes, and bad odors in the paper as well as web breaksxe2x80x94costly disruptions in paper machine operations.
Biofouling of recreational waters such as pools or spas or decorative waters such as ponds or fountains can severely detract from people""s enjoyment of them. Biological fouling often results in objectional odors. More importantly, particularly in recreational waters, biofouling can degrade the water quality to such an extent that it becomes unfit for use and may even pose a health risk.
Sanitation waters, like industrial process waters and recreational waters, are also vulnerable to biofouling and its associated problems. Sanitation waters include toilet water, cistern water, septic water, and sewage treatment waters. Due to the nature of the waste contained in sanitation waters, these water systems are particularly susceptible to biofouling.
To control biofouling, the art has traditionally treated an affected water system with chemicals (biocides) in concentrations sufficient to kill or greatly inhibit the growth of biofouling organisms. See, e.g., U.S. Pat. Nos. 4,293,559 and 4,295,932. For example, chlorine gas and hypochlorite solutions made with the gas have long been added to water systems to kill or inhibit the growth of bacteria, fungi, algae, and other troublesome organisms. However, chlorine compounds may not only damage materials used for the construction of aqueous systems, they may also react with organics to form undesirable substances in effluent streams, such as carcinogenic chloromethanes and chlorinated dioxins. Certain organic compounds, such as methylenebisthiocyanate, dithiocarbamates, haloorganics, and quaternary ammonium surfactants, have also been used. While many of these are quite efficient in killing microorganisms or inhibiting their growth, they may also be toxic or harmful to humans, animals, or other non-target organisms.
One possible way to control the biofouling of aqueous systems, which include the associated submerged surfaces, would be to prevent or inhibit bacterial adhesion to submerged surfaces within the aqueous system. This can be done, of course, using microbicides which, however, generally suffer from some of the disadvantages mentioned above. As an alternative, the present invention provides methods and compositions useful to substantially inhibit bacterial adhesion to a submerged or submergible surface and in controlling biofouling of aqueous systems. The invention obviates the disadvantages of prior methods. Other advantages of this invention will become apparent from a reading of the specifications and appended claims.
2. Field of the Invention
The invention uses a sulfamic acid or a salt thereof to inhibit bacterial adhesions to submergible or submerged surfaces, particularly those surfaces within an aqueous system. The invention also relates to methods and compositions for controlling biological fouling.
The invention relates to a method to inhibit bacteria from adhering to a submergible surface. The method contacts the submergible surface with an effective amount of at least one sulfamic acid or a salt thereof to inhibit bacteria from adhering to a submergible surface. The sulfamic acid used in the method has the following formula R1R2NS(O)2(OH). In this formula, R1 and R2 are, independently, a hydrogen, a C4-C20 alkyl group or a cyclohexyl group. However, R1 and R2 are not both hydrogen. Alternatively, R1 and R2 together with the N may also form a 5-8 membered heterocyclic ring having the formula: 
In the heterocyclic ring, X is O, NH, or CH2. The dashed lines indicate that the group X may occupy different positions in a particular heterocyclic ring.
The invention relates also to a method for controlling biofouling of an aqueous system.
This method adds to an aqueous system an effective amount of at least one sulfamic acid, described above, or salt thereof to inhibit bacteria from adhering to submerged surfaces within the aqueous system. This method effectively controls biofouling without substantially killing the bacteria.
The invention also relates to a composition for controlling biofouling of an aqueous system. The composition comprises at least one sulfamic acid or a salt thereof in an amount effective to inhibit bacteria from adhering to a submergible surface or a submerged surface within the aqueous system.
Not Applicable
In one embodiment, this invention relates to a method to inhibit bacteria from adhering to a submergible surface. A submergible surface is one which may be at least partially covered, overflowed, or wetted with a liquid such as water or another aqueous fluid or liquid. The surface may be intermittently or continually in contact with the liquid. As discussed above, examples of submergible surfaces include, but are not limited to ship or boat hulls, marine structures, teeth, medical implants, surfaces within an aqueous system such as the inside of a pump, pipe, cooling tower, or heat exchanger. A submergible surface may be composed of hydrophobic, hydrophilic, or metallic materials. Advantageously, using a sulfamic acid or salt thereof according to the invention can effectively inhibit bacteria from adhering to hydrophobic, hydrophilic, or metallic submergible or submerged surfaces.
To inhibit the adhesion of a bacteria to a submergible surface, the method contacts the submergible surface with a sulfamic acid or salt thereof. The surface is contacted with an effective amount of a sulfamic acid or salt thereof, or mixture of sulfamic acids or salts thereof, to inhibit microorganism adhesion to the surface. Preferably, a sulfamic acid or its salt is applied as a pretreatment of the submergible surface prior to submerging in an aqueous system. The sulfamic acid or salt thereof may be applied to the submergible surface using means known in the art. For example, as discussed below, the sulfamic acid or salt thereof may be applied by spraying, coating or dipping the surface with a liquid formulation containing the sulfamic acid or salt thereof. Alternatively, the sulfamic acid or salt thereof may be formulated in a paste which is then spread or brushed on the submergible surface. Advantageously, the sulfamic acid or salt thereof may be a component of a composition or formulation commonly used with a particular submergible surface.
xe2x80x9cInhibiting bacteria from adheringxe2x80x9d to a submergible surface means to allow a scant or insignificant amount of bacterial adhesion for a desired period of time. Preferably, essentially no bacterial adhesion occurs and more preferably, it is prevented. The amount of sulfamic acid or salt thereof employed should allow only scant or insignificant bacterial adhesion and may be determined by routine testing. Preferably, the amount of sulfamic acid or salt thereof used is sufficient to apply at least a monomolecular film of sulfamic acid or salt thereof to the submergible surface. Such a film preferably covers the entire submergible surface.
Contacting a submergible surface with a sulfamic acid or salt thereof according to this method allows the surface to be pretreated against bacterial adhesion. Accordingly, the surface may be contacted with a sulfamic acid or salt thereof then submerged in the aqueous system.
The present invention relates also to a method for controlling biofouling of an aqueous system. An aqueous system comprises not only the aqueous fluid or liquid flowing through the system but also the submerged surfaces associated with the system. Submerged surfaces are those surfaces in contact with the aqueous fluid or liquid. Like the submergible surfaces discussed above, submerged surfaces include, but are not limited to, the inside surfaces of pipes or pumps, the walls of a cooling tower or headbox, heat exchangers, screens, etc. In short, surfaces in contact with the aqueous fluid or liquid are submerged surfaces and are considered part of the aqueous system.
The method of the invention adds at least one sulfamic acid or salt thereof to the aqueous system in an amount which effectively inhibits bacteria from adhering to a submerged surface within the aqueous system. At the concentration used, this method effectively controls biofouling of the aqueous system without substantially killing the bacteria.
xe2x80x9cControlling biofoulingxe2x80x9d of the aqueous system means to control the amount or extent of biofouling at or below a desired level and for a desired period of time for the particular system. This can eliminate biofouling from the aqueous system, reduce the biofouling to a desired level, or prevent biofouling entirely or above a desired level.
According to the present invention, xe2x80x9cinhibiting bacteria from adheringxe2x80x9d to a submerged surface within the aqueous system means to allow a scant or insignificant amount of bacterial adhesion for a desired period of time for the particular system. Preferably, essentially no bacterial adhesion occurs and more preferably, bacterial adhesion is prevented. Using a sulfamic acid or salt thereof according to the invention can, in many cases, break up or reduce other existing attached microorganisms to undetectable limits and maintain that level for a significant period of time.
While some sulfamic acids or salts thereof may exhibit biocidal activity at concentrations above certain threshold levels, sulfamic acids or salts thereof effectively inhibit bacterial adhesion at concentrations generally well below such threshold levels. According to the invention, the sulfamic acid or salt thereof inhibits bacterial adhesion without substantially killing the bacteria. Thus, the effective amount of a sulfamic acid or salt thereof used according to the invention is below its toxic threshold, if the sulfamic acid or salt thereof also has biocidal properties. For example, the concentration of the sulfamic acid or salt thereof may be ten or more times below its toxic threshold. Preferably, the sulfamic acid or salt thereof should also not harm non-target organisms which may be present in the aqueous system.
A sulfamic acid or salt thereof, or a mixture of sulfamic acids or salts thereof, may be used to control biofouling in a wide variety of aqueous systems such as those discussed above. These aqueous systems include, but are not limited to, industrial aqueous systems, sanitation aqueous systems, and recreational aqueous systems. As discussed above, examples of industrial aqueous systems are metal working fluids, cooling waters (e.g., intake cooling water, effluent cooling water, and recirculating cooling water), and other recirculating water systems such as those used in papermaking or textile manufacture. Sanitation aqueous systems include waste water systems (e.g., industrial, private, and municipal waste water systems), toilets, and water treatment systems, (e.g., sewage treatment systems). Swimming pools, fountains, decorative or ornamental pools, ponds or streams, etc., provide examples of recreational water systems.
The effective amount of a sulfamic acid or salt thereof to inhibit bacteria from adhering to a submerged surface in a particular system will vary somewhat depending on the aqueous system to be protected, the conditions for microbial growth, the extent of any existing biofouling, and the degree of biofouling control desired. For a particular application, the amount of choice may be determined by routine testing of various amounts prior to treatment of the entire affected system. In general, an effective amount used in an aqueous system may range from about 1 to about 500 parts per million and more preferably from about 20 to about 100 parts per million of the aqueous system.
The sulfamic acids or salts thereof employed in the present invention have the following general formula R1R2NS(O)2(OH). In this formula, R1 and R 2 are, independently, a hydrogen, a C4-C20 alkyl group or a cyclohexyl group. But, R1 and R 2 are not both hydrogen.
Preferably, R1 is a C5-C20 alkyl group and R2 is a hydrogen. When R1 and R 2 is an alkyl group, it is preferably a C8-C18 alkyl group, more preferably, a C10-C14 alkyl group, and most preferably a C12 alkyl group. The alkyl group may be bound through a terminal carbon or a carbon in the alkyl chain. The alkyl group may contain carbon-carbon double or triple bonds and may also be branched or unbranched.
Alternatively, R1 and R2 together with the N may also form a 5-8 membered heterocyclic ring having the formula: 
In the heterocyclic ring, X is O, NH, or CH2. The dashed lines indicate that the group X may occupy different positions in a particular heterocyclic ring. Preferably, the heterocyclic ring is 5- or 6-membered ring. Specific preferred rings include morpholinyl and piperidinyl.
Specific preferred sulfamic acids of the above formula include butyl sulfamic acid, compound (a); amyl sulfamic acid, compound (b); octyl sulfamic acid, compound (c); dioctyl sulfamic acid, compound (d); dodecyl sulfamic acid, compound (e); didodecyl sulfamic acid, compound (f); octadecyl sulfamic acid, compound (g); dicyclohexyl sulfamic acid, compound (h); morpholino sulfamic acid, compound (i); and piperidinyl sulfamic acid, compound (j).
Sulfamic acids or salts thereof useful in the invention are available either commercially from chemical supply houses or may be prepared from starting materials using well-known literature methods. For example, a sulfamic acid or salt thereof may be prepared by the following method. An amine is dissolved in a dry solvent, such as THF, and chilled in an ice bath. An acid, such as chlorosulfonic acid, is added dropwise to the amine in an equimolar amount, i.e. 1 mol of acid per 1 mol of amine. After the reaction is complete, the solvent was removed by rotary evaporation. The sulfamic acid or salt thereof is collected by filtration and washed with water. Methods for the preparation of various sulfamic acids or salts thereof are described in Nickless, G. Inorganic Sulphur Chemistry, Elsevier Publishing Company, New York; 611-614 (1968).
Salts of sulfamic acids can also be used in the invention. Sulfamic acids are amphoteric, i.e. exhibit both acidic and basic properties. Accordingly, two types of sulfamic acid salts can be formed: a salt of the acid moiety and a salt of the basic or nitrogen moiety. Salts of the acid moiety (referred to as xe2x80x9cacid saltsxe2x80x9d) include, but are not limited to, alkali metal and quaternary ammonium salts. Salts of the basic or nitrogen moiety (referred to as xe2x80x9cquaternized sulfamic acid saltsxe2x80x9d) have the following general formula: R1R2R3N+S(O)2 (OH) where R1 and R2 are as defined above and R3 is, for example, a hydrogen or a C1-C20 alkyl group, such as discussed above.
The methods according to the invention may be part of an overall water treatment regimen. The sulfamic acid or salt thereof may be used with other water treatment chemicals, particularly with biocides (e.g., algicides, fungicides, bactericides, molluscicides, oxidizers, etc.), stain removers, clarifiers, flocculants, coagulants, or other chemicals commonly used in water treatment. For example, submergible surfaces may be contacted with a sulfamic acid or salt thereof as a pretreatment to inhibit bacterial adhesion and placed in aqueous system using a microbicide to control the growth of microorganisms. Or, an aqueous system experiencing heavy biological fouling may first be treated with an appropriate biocide to overcome the existing fouling. A sulfamic acid or salt thereof may then be employed to maintain the aqueous system. Alternatively, a sulfamic acid or salt thereof may be used in combination with a biocide to inhibit bacteria from adhering to submerged surfaces within the aqueous system while the biocide acts to control the growth of microorganisms in the aqueous system. Such a combination generally allows less microbicide to be used.
xe2x80x9cControlling the growth of the microorganismsxe2x80x9d in an aqueous system means control to, at, or below a desired level and for a desired period of time for the particular system. This can be eliminating the microorganisms or preventing their growth in the aqueous systems.
The sulfamic acid or salt thereof may be used in the methods of the invention as a solid or liquid formulation. Accordingly, the present invention also relates to a composition containing a sulfamic acid or salt thereof. The composition comprises at least one sulfamic acid or salt thereof in an amount effective to inhibit bacteria from adhering to a submergible surface or a submerged surface within an aqueous system. When used in combination with another water treatment chemical such as a biocide, the composition may also contain that chemical. If formulated together, the sulfamic acid or salt thereof and water treatment chemical should not undergo adverse interactions that would reduce or eliminate their efficacy in the aqueous system. Separate formulations are preferred where adverse interactions may occur.
Depending on its use, a composition according to the present invention may be prepared in various forms known in the art. For example, the composition may be prepared in liquid form as a solution, dispersion, emulsion, suspension, or paste; a dispersion, suspension, or paste in a non-solvent; or as a solution by dissolving the sulfamic acid or salt thereof in a solvent or combination of solvents. Suitable solvents include, but are not limited to, acetone, glycols, alcohols, ethers, or other water-dispersible solvents. Aqueous formulations are preferred.
The composition may be prepared as a liquid concentrate for dilution prior to its intended use. Common additives such as surfactants, emulsifiers, dispersants, and the like may be used as known in the art to increase the solubility of the sulfamic acid or its salt as well as other components in a liquid composition or system, such as an aqueous composition or system. In many cases, the composition of the invention may be solubilized by simple agitation. Dyes or fragrances may also be added for appropriate applications such as toilet waters.
A composition of the present invention may also be prepared in solid form. For example, the sulfamic acid or salt thereof may be formulated as a powder or tablet using means known in the art. The tablets may contain a variety of excipient known in the tableting art such as dyes or other coloring agents, and perfumes or fragrances. Other components known in the art such as fillers, binders, glidants, lubricants, or antiadherents may also be included. These latter components may be included to improve tablet properties and/or the tableting process.